1. Field of the Invention
The present invention relates to a liquid composition, a method of producing a silicon substrate, and a method of producing a liquid discharge head substrate.
2. Description of the Related Art
In recent years, various silicon devices have been applied to a variety of devices such as liquid discharge heads, thermosensors, pressure sensors, and acceleration sensors with developments of micromachining technologies. These various silicon devices are desired to satisfy various demands on production cost reduction, miniaturization, and higher functions. For satisfying these demands, fine processing technologies which are micromachining technologies are used in the production of these silicon devices. In these micromachining technologies, anisotropic silicon wet etching technologies are used to form a desired structure and, for example, a method is used in which silicon is etched by using an alkaline etching solution which is an aqueous solution of potassium hydroxide or tetramethylammonium hydroxide.
However, because a long time is required for anisotropic silicon wet etching, it is desired to shorten the time required for silicon etching to improve productivity from the reason that production time is determined by the etching time. Japanese Patent Application Laid-Open No. 2009-206335 discusses that an etching solution containing an alkaline organic compound, sodium hydroxide, and a silicon-containing compound is used to improve silicon etching rate.
However, there is a possibility that the liquid composition discussed in Japanese Patent Application Laid-Open No. 2009-206335 fails to facilitate the formation of a desired shape when it is applied to a method of producing a silicon device using a silicon oxide film as an etching mask because a difference in etching rate between silicon oxide and silicon is insufficient.